<script language="JavaScript">

 <!--

 var srcX = 1024; //原图长宽

 var srcY = 768;

 var bigX = 500; //原比例预览大小,可以设置成任意大小

 var bigY = 300;

 var smallX = 256; //缩略图大小,要与原大小成比例

 var smallY = 192;

 var viewX = bigX / srcX * smallX; //预览范围

 var viewY = bigY / srcY * smallY;

 var bl = srcX / smallX;//缩小比例

 var border = 8; //边框

 window.onload=function (){

     bigbox.style.borderWidth=border;

     bigbox.style.width=bigX+border*2;

     bigbox.style.height=bigY+border*2;

     smallpic.width=smallX;

     smallpic.height=smallY;

     view.style.width=viewX;

     view.style.height=viewY;

     smallbox.style.borderWidth=border;

     if (window.event){

         smallbox.style.width=smallpic.offsetWidth+border*2;

         smallbox.style.height=smallpic.offsetHeight+border*2;

     }else{

         smallbox.style.width=smallpic.offsetWidth;

         smallbox.style.height=smallpic.offsetHeight;

     }

     move(event);

 }

 function move(e){

     var e = window.event?window.event:e;

     var iebug = 0;

     if (window.event){

         var vX = e.offsetX - viewX/2;

         var vY = e.offsetY - viewY/2;

     }else{

         var vX = e.pageX - viewX/2 - smallbox.offsetLeft - border;

         var vY = e.pageY - viewY/2 - smallbox.offsetTop - border;

         iebug = 2;

     }

     if (vX < 0) vX = 0;

     if (vY < 0) vY = 0;

     if (vX > smallX - viewX - iebug) vX = smallX - viewX - iebug;

     if (vY > smallY - viewY - iebug) vY = smallY - viewY - iebug;

     view.style.left = vX + smallbox.offsetLeft + border;

     view.style.top = vY + smallbox.offsetTop + border;

     bigbox.style.backgroundPosition= - vX * bl + " " + -vY * bl;

 }

 //-->

 </script>

 <style type="text/css">

 <!--

 *{padding:0;margin:0}

 img{display:block;}

 #smallbox{border:1px #c33 solid;float:left;width:0;height:0;overflow:hidden}

 #bigbox{border:1px #c33 solid;width:0px;height:0px;float:left;background:url('/upload/20071130224657571.jpg') no-repeat;}

 #view{border:1px #ddd solid;width:0px;height:0px;position:absolute}

 .head{text-align:center;line-height:40px;font:bold 16px/40px;color:red}

 //-->

 </style>

 <div class="head">图片放大效果</div>

 <div id="smallbox"><img id="smallpic" src="/upload/20071130224657571.jpg" border="0" onmousemove="move(event)"></div>

 <div id="bigbox"></div>

 <div id="view"></div>